Incandescent electric lamp



1966 w. SCHILLING ETAL 3, 7, 0

INCANDESGENT ELECTRIC LAMP Filed Dec. 30, 1963 mWwwW m "WMWWW 2 Fig.7

INVENTORS Dr. Werner Schilling Jijrgen Sanden ATTORNEY United States Patent 3,227,909 INCANDESCENT ELECTRIC LAMP Werner Schilling and Jurgen Sanden, Heidenheim (Brenz), Germany, assignors to Patent-Treuhand-Gesellschaft fiir Electrische Gluhlampen m.b.H., Munich, Germany Filed Dec. 30, 1963, Ser. No. 334,357 Claims priority, application Germany, Jan. 3, 1963, P 30,894 6 Claims. (Cl. 313-315) The present invention relates to a gas-filled low voltage lamp by which is meant a lamp rated at a voltage up to sixty volts such as generally operated from batteries. Lamps of this type are used with vehicles of all kinds, and the lamps herein described relate to those intended particularly for utilization as vehicle headlights.

It is proposed in connection with the present invention to employ in the lamp bulb or envelope, an addition of iodine with the gas filling sealed in the bulb, notwithstanding failure of prior efforts of this nature. In favor of the iodine additive, it may be said that use thereof obtains a very high light output, and an output that maintains a constancy during the life of the lamp, and for the output obtained the lamp may be relatively small in size. However, when iodine is used, the entire inner lamp surface must be maintained, by heat from the filament, at least at 250 C., and in such manner that there are no spots or sections of the inner bulb surface at a less temperature. It would seem, at first thought, that a cylindrical bulb with a coaxial filament would satisfy the requirement, but attempts at using such an assembly develops the adverse circumstance that the hollow cylindrical surface of a bulb so formed and functioning as a reflector, emits light in undesired directions and with considerable intensity, in addition to the light beams directed as desired. Causes for such troubles are refractions and reflections, partly multiple reflections, in and from the cylindric bulb wall. Coatings on the envelope inner wall to prevent the undesired reflections cannot be used because of the aggressiveness of iodine vapor which is ruinous to any proposed coatings. Neither is it practical to use coatings on the outer wall of the bulb, because of the high temperature to be contended with and because of the expense involved both of material and labor, and for other good and suficient reasons not believed necessary to expound upon herein.

In general terms, therefore, the fundamental object of the present invention is to provide a practical lamp adapted to utilize the benefits of iodine additive to the vapor filling therein.

Also in its broad aspect, the invention proposes a lamp capable of high intensity concentrated light output with a low voltage input.

Somewhat more specifically the invention contemplates a lamp wherein the bulb or envelope can be made of a single material throughout, unaffected by the iodine additive to the gaseous filling.

Still more specifically, the invention provides an envelope providing relatively close proximity of the filament to the envelope wall.

Another object of the invention is to establish a rela tionship between the filament and the area for concentrated light projection from the envelope, to produce maximum emission of light from the filament and through 3,227,909 Patented Jan. 4, 1966 said area, and avoid undue refractions and disturbing reflections.

More specifically, the invention provides a filament of planar characteristic and an envelope with a light-projection area substantially in parallelism to the planar facet of the filament.

Other objects, advantages and novel structural features will appear to persons skilled in the art to which the invention appertains, as the description proceeds, both by direct reference thereto and by implication from the context.

Referring to the accompanying drawing, in which like numerals of reference indicate similar parts throughout the several views;

FIGURE 1 is a longitudinal section of a lamp disclosing one form of the invention;

FIGURE 2 is a front end view of the lamp of FIG. 1;

FIGURE 3 is a longitudinal section of a lamp illustrative of a second form of the invention;

FIGURE 4 is a front view of the lamp of FIG. 3;

FIGURE 5 is a longitudinal section of a third form of the invention;

FIGURE 6 is a front view of the lamp of FIG. 5; and

FIGURE 7 is a cross-section of a lamp envelope and filament of a fourth form of the invention, longitudinal section whereof may be as shown by the form of FIG. 5.

Giving attention initially to the showing of the lamp of the present invention illustrated in FIGS. 1 and 2, a hollow bulb 1 is shown, the same being made from a transparent or other light-transmitting high-melting material, such as quartz or hard glass. At what is herein termed the front of the lamp (shown at the bottom of FIG. 1) the bulb provides a flat area 2 through which concentration of light is to pass in use of the lamp, in a direction perpendicular to that flat area. This will provide a concentrated beam completely avoiding refraction in its passage through the said area. Except for this flat area, the interior of the bulb is approximately spherical.

Within the bulb, substantially including the geometric center of the spherical configuration mentioned, is a filament of tungsten or other suitable material. The filament is a longitudinally straight fiat core wire coil, thereby having a planar characteristic, so that when viewed in plan it has an extensive planar facet, but when viewed at a position of rotation from plan view, it

exhibits only a very narrow edge. The narrow edge of the filament appears in FIG. 1, whereas the extenisve planar facet appears in FIG. 2.

The planar facet of the filament 3 is situated in the bulb 1 parallel to the flat area 2 at the front of the bulb, in consequence of which the light rays from the filament pass to and through said fiat area in a direction perpendicular thereto without refraction. Such reflection as may take place from said fiat area, returns into the filament itself. Thus, by this construction, refraction and distributing reflections are eliminated.

It should also be noted that since the flat facet of the filament is in a plane parallel to the flat area 2 of the bulb 1, there is a constancy of distance of all points of the filament from the said fiat area of the bulb. Also the ends of the filament are substantially the same distance from the proximate spherical portion of the bulb wall opposite to said ends as the distance from the filament to the flat area of the bulb. By locating the filament substantially in a diametric plane of the bulb, the distance behind the filament to the spherical wall likewise is sufficiently close thereto so as to keep that part of the bulb hot. Thus the requirement that all points of the inner surface of the envelope wall are located as near as possible to the filament is fulfilled. The envelope or bulb wall is kept in operation by the filament at temperatures at or above 250 required by the iodine cycle.

The filament 3 is supported at its ends by tungsten inlead wires 4 within the bulb and located perpendicular to the planar facet of the filament, being welded or otherwise unified with intermediate in-lead sections 5 interposed between the respective inner in-leads 4 and respective outer in-leads 6 alined therewith. The inner in-leads 4 and the outer in-leads 6 are relatively rigid, whereas the intermediate section 5 may be more, flexible to accommodate it to sealing-in operation and to expansion and contraction of the lamp material. It is chosen from the group of materials having a coefficient of expansion of the bulb material to maintain a positive seal, molybdenum foil being an acceptable example. The outer in-lead 6 correspondingly may be molybdenum wire. The said intermediate section 5 and adjacent ends welded thereto of the inner and outer in-leads 4 and 6 are embedded and sealed in the press 7 of the lamp in accordance with usual lamp manufacturing operations. An appropriate exhaust channel 8 is provided longitudinally of the press 7, by which exhaust and ultimate charging with gas and the iodine is effected. Examples of acceptable gas filling with which iodine may be used, may be selected from the group comprising nitrogen, argon, krypton, and xenon. Cold filling pressure satisfactorily employed for introduction of any of these gases is preferably between one and twenty atmospheres.

There are instances when it is desirable to provide lamps the light from which may be projected both at the front and back thereof, and lamps having this qualification are illustrated in the modifications of FIGS. 3-7. In each instance these lamps have two presses projecting at diametrically opposite sides of the hollow body portion and of less thickness than the distance between the flattened areas.

Considering the disclosures of FIGS. 3 and 4, the hollow envelope or bulb 11 has its front and back flattened to provide areas 12, 12 parallel to each other through which light may be projected both forwardly and rearwardly of the lamp in a direction perpendicular to said areas. In this showing, the hollow body, except for flattening of the two opposite areas, has an internal spherical configuration. Within the bulb hollow, substantially midway between and parallel to said flattened areas 12, 12, there is a flat filament 13 description whereof conforms in its entirety with the previously identified filament 3 explained at length hereinabove, so will not be repeated here. The ends of said filament are welded, as before, to contiguous ends projecting into the bulb of inner in-leads 14 of tungsten wire, but in this instance said in-leads and the filament are alined. An intermediate i'n-lead section 15 of molybdenum foil isinterposed, as in the previously described construction, between said inner in-lead 14 and an alined outer in-lead 16 of molybdenum wire and unified with both, as by being Welded thereto. The foil is thin and flat, and its flat face is in the same plane as the flat facet of the filament as may be seen in FIG. 4. The thin edges of the foil and filament appear in FIG. 3.

In order to maintain the front and back flattened areas 12, 12 unobstructed, and to maintain the flat facet of the filament midway between and parallel to said areas, diametrically opposite presses 17 project from the sides of the bulbous body of the lamp. These presses are flattened in the same direction as the bulbous body is flattened, and to a less thickness so as to lie inbetween planes of said flattened areas 12, 12. At another side of the bulbous body, a tubulation is originally present for purpose of evacuation of the envelope and recharging it with one of the aforementioned gases and with the iodine, after which the tubulation is tipped off as shown at 18 in FIG. 4.

The lamp shown in FIGS. 5, 6 and 7 consists of an initially cylindrical bulb 21 flattened on two diametrically opposite sides chordally of the cylinder to form the front and back areas 22 in substantially parallel planes. A straight flat core wire coil filament as heretofore described, and here designated by numeral 23, coincides longitudinally at its axis with the cylinder axis. The filament is rated at eight volts and fifty-five watts. The current in-leads consisting of three sections 24, 25, 26, conforming to in-leads described in connection with the preceeding forms of the invention, are sealed in two outer stem presses 27 the flat sides of which lie between the planes of the chordal flat areas 22 of the bulb. Thus in the lamp of these several figures, as well as with the lamp of FIGS. 3 and 4, the planes of the flattened areas of the bulb, of the flat areas of the stem presses, of the flat facet of the filament, and the flat molybdenum foil section of the in-leads, are all in substantial parallelism. Light rays from the flat facet of the filament pass through the flat areas in a direction perpendicular to both the front and back flattened areas 22 of the bulb. It may be added here, that the bulb as manufactured has a length of about 35 mm., greatest diameter of 10 mm., and smallest diameter between the flattened areas of 5.5 mm. Tubulat-ion seal-off or tip 28 completes the lamp after the gas filling, with iodine additive are introduced at the cold filling pressure previously mentioned herein.

Partial flattening of circular cylindric bulbs may be employed with a degree of accomplishment of the objects of the invention, and so made the bulb then will have an oval cross-section as shown in FIG. 7. This cross section shows also that the distance between the inner bulb wall and the flat core coil is quite similar in all directions and is very small.

Finally, it may be said that lamps according to the disclosed invention with straight flat core coil filaments supported only at their ends by the two in-leads, and at approximately constant spacing from the bulb wall, may be made for inputs up to about 1000 watts. While lamps of this invention have been described as having utility in the automotive trade, it is to be understood that use is not restricted thereto.

We claim:

1. An electric incandescent lamp having a hollow bulb of high-melting material and having a pair of in-leads sealed in said bulb, a tungsten filament in the form of a coil longitudinally of an axis, said coil comprised of substantially flat convolutions presenting as a group a filament with broad planar facets and narrow edges longitudinally of said axis and with said broad facets and narrow edges spaced from said axis, said filament being supported entirely by said pair of in-leads, said bulb having a gas filling with additive of iodine thereto, and said bulb having a flattened area a midportion whereof is directly opposite to and in a plane in approximate paral lelism to a said planar facet of the filament, thereby obtaining a broad source of light projection directly from said planar facet perpendicular to and through said flattened area and yet avoiding refraction and reflection of light from the filament in transition to and through said flattened area of the bulb.

2. An incandescent lamp in accordance with claim 1, wherein the bulb is inpart sphere shaped with said flattened area on one side and with the diameter of said area exceeding the length and breadth of said planar facets of the filament.

3. An incandescent lamp in accordance with claim 1, wherein the bulb is cylindrically shaped with said flattened area on one side, the axis of said cylinder and the axis of said filament being parallel.

4. An incandescent lamp in accordance with claim 1, wherein the bulb is spherically shaped with flattened areas on two sides in parallel planes.

5. An incandescent lamp in accordance with claim 1, wherein the bulb is cylindrically shaped with flattened areas on two opposite sides in parallel planes, and with the axis of the filament coinciding with the axis of the bulb.

6. An incandescent lamp in accordance with claim 1, wherein the bulb is cylindrically shaped with flattening longitudinally to an oval cross-section, and with the axis of the filament coinciding with the axis of the bulb.

References Cited by the Examiner UNITED STATES PATENTS 3,067,357 12/1962 Fridrich 313-184 X FOREIGN PATENTS 1,203,844 8/1959 France.

91,056 12/1921 Switzerland.

10 ROBERT SEGAL, Primary Examiner.

S. D. SCHLOSSER, Examiner. 

1. AN ELECTRIC INCANDESCENT LAMP HAVING A HOLLOW BULB OF HIGH-MELTING MATERIAL AND HAVING A PAIR OF IN-LEADS SEALED IN SAID HUB, A TUNGSTEN FILAMENT IN THE FORM OF A COIL LONGITUDINALLY OF AN AXIS, SAID COIL COMPRISED OF SUBSTANTIALLY FLAT CONVOLUTIONS PRESENTING AS A GROUP A FILAMENT WITH BROAD PLANAR FACETS AND NARROW EDGES LONGITUDINALLY OF SAID AXIS AND WITH SAID BROAD FACETS AND NARROW EDGES SPACED FROM SAID AXIS, SAID FILAMENT BEING SUPPORTED ENTIRELY BY SAID PAIR OF IN-LEADS, SAID BULB HAVING A GAS FILLING WITH ADDITIVE OF IODINE THERETO, AND SAID BULB HAVING A FLATTENED AREA A MIDPORTION WHEREOF IS 